These are from a practice exam, I've already narrowed down my answers, these are the ones I'm not sure about.THANKS.

The tissue type repsonsible for protection of the body from the external environment?-skin, epithelium or integument?

I am thinking epithehelium--------------------------------------------------------------Which best explains why long bones are hollowin themiddle?- lighten them, Wolff's law (absence of load)?-------------------------------------------------------------------------------------------Which about collagen is FALSE?- formed by macromolecular assembly of procallagen, produced by enzymes, or its slight crimp give it elasticity independent of elastin?----------Which is false?- primary cell in fibrocaritlage is fibrochondrocyte or , primary celll type in skeletal muscle is myofibre?-------------------------------------------------------------------------Which tissue best resit tensile pure force?- tendon, muscle elastic cartilage or fibrocartilage?--------------------------------------Which does not describe how animal reduce heat loss in cold environment?- brown adpose tissu, or decrease body temp or countercurrent mechanisms?